Polyolefins stabilized with 2, 6-ditertiary butyl-p-cresol and organic sulfides



United States Patent 3,258,449 POLYGLEFINS STABILIZED WITH 2,6-DITERTI-ARY BUTYL-p-CRESOL AND ORGANIC SUL- FIDES Claus Heuck, Hotheirn, Taunus,Otto Mauz, Frankfurt am Main, Jakob Winter, Hofheim, Taunus, and FelixSchuide, Neuenhain, Taunus, Germany, assignors to Farbwerke HoechstAktiengesellschaft vormals Meister Lucius & Iii-lining, Frankfurt amMain, Germany, a corporation of Germany No Drawing. Filed lune 2, 1960,Ser. No. 33,393 Claims priority, applicatign germany, June 10, 1959, F 4

2 Claims. 01. zen-45.95

The present invention relates to a process for improving polyolefins.

Many highly polymeric compounds undergo degradation under the action ofoxygen at elevated temperatures, particularly under the influence oflight. In the course of this degradation, the physical properties of thestarting product, such as the strength, elongation or hardness of theproduct, may deteriorate such that it can no longer be used forindustrial purposes. In order to prevent such a degradation, there maybe applied numerous improving agents called stabilizers.

Thus phenols and phenol derivatives, for example on the basis of4,4dihydroxy-diphenylmethane or 4,4-dihydroxy-dimethylmethane have beendescribed to be particularly effective age resisters, for example forhighpressure (branched) polyolefins and low-pressure (linear)polyolefins. There are also cited in 'various patents aminophenols andsulfurous phenol derivatives obtained by condensing alkyl phenols withmonosulfur dichloride or disulfur dichloride.

However, the aforementioned age resisters have-incontaining 1 to 31carbon atoms, further by aromatic or araliphatic radicals.

These dialkyl sulfides which may be prepared in known and simple manner,for example, from alkyl halides, such as amyl-, hexyl-, octyl-,dodecy1-, hexadecyl-, octadecyl-, eicosyland myricyl-chloride, andsodium sulfide produce, when applied as such, none or only aninsignificant resistance to aging in the various polyolefins.

When combining these dialkyl sulfides with a phenolic age resister,however, a synergistic effect is produced raising the age resistance ofthe phenolic substances in an unexpected manner.

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According to present knowledge, there may be distinguished tWo types ofstabilizers or age resisters with respect to their efiicacy:

(a) Substances having a specific action as antioxidants,

(b) Substances which, as such, are not effective as antioxidants or onlyin a low degree but which, in mixture with compounds of group (a),appreciably enhance the efficacy (so-called costabilizers).

The antioxidants bring about the discontinuance of the chain reaction ofthe ant-oxidation by intercepting and rendering harmless the radicalsformed in the course of (this process. These antioxidants generally havea phenolic structure.

The substances of group (b) having a synergistic action exhibit, whenapplied as such, none or only an insignificant age resisting action;however, they increase the action of the antioxidants mentioned in group(a) in a high degree. They can regenerate the antioxidants which aregradually used up by oxidation, and likewise render harmless the tracesof metal compounds that have .a prooxidative action by the formation ofsalts or by chelation.

As phenolic components there were applied alkylated phenols,condensation products of monoalkyl phenols and dialkyl phenols, withaldehydes and ketones, such as orthocresol, tertiary butyl phenol, nonylphenol, nonyl paracresol, thymol, 2,4-di-tertiary-butyl phenol,Z-methyl-4-tertiary-butyl phenol, 2,4-di-i-octyl phenol, 2,4-di-inonlyphenol etc. with formaldehyde, propion-aldehyde or acetone,cyclohexanone, etc.

In order to increase the stabilizing action as a costabilizer, analiphatic or aromatic sulfide is added to the phenolic component. Thesulfide can, in the simplest case, have a symmetric structure, RS-R, inwhich R is an aliphatic radical containing 4 to 25 carbon atoms, ahydroaromatic or aromatic hydrocarbon radical.

The sulfide may also have an asymmetric structure according to theformula RSR, in which R and R are aliphatic radicals containing 4- to 25carbon atoms, hydroaromatic or aromatic hydrocarbon radicals ofdifferent constitution; or R represents an aliphatic hydrocarbon chainand R a hydroaromatic hydrocarbon-, benzene-, thiophene-,naphthalene-nucleus, or a higher condensed nucleus.

Moreover, there can also be contained in the molecule several sulfuratoms which are, however, separated by carbon atoms. These compoundshave the general formula:

in which R is a hydrocarbon radical of a hydroaromatic or aromaticnature containing 4 to 25 carbon atoms, and R is a hydrocarbon radical,while the subscript n has a value of 1 to 20. R may also contain heteroatoms,

such as oxygen, nitrogen, etc., for example the following groups:

or it may be a benzene-, thiophene-, naphthaleneor anthracene-nucleus,as well as hydrogenated nuclei which may, in addition, be alkylated.

Compounds of this kind are obtained by reacting with mercaptans dia-lkylhalides, such as dichloromethane, 1,2- dichloroethane,1,3-dichloropropane, 1,4-dichlorobutane or fi,,8'-dichlorodiethyl ether,bis-(chloromethyl)naphthalene, bis-(chloromethyl)-thiophene,dichloropentamethylbenzene, 1,4-di-(chloromethyl)-benzene, etc.

If, furthermore, mercaptans are reacted with, for example, carbontetrachloride, tetrachloroethane, hexachloroethane, compounds areobtained containing in the molecule an even greater number of sulfuratoms and which, in combination with phenolic age resisters, yield avery good synergistic eifect.

With regard to compatibility, sulfides carrying long aliphatichydrocarbon radicals, such as octyl radicals, do decyl radicals andoctadecyl radicals, are especially efiective for the stabilization ofpolyolefins, such as polyethylene, polypropylene, polybutene andpolymethylpentene.

The total amount of age resisters and costabilizers required amounts ingeneral in the case of normally stressed shaped articles to 0.001 to 5%,preferably 0.05 to 1%. The two components should be used in the ratio of5 :1 to 1:5 parts by weight, preferably 1:1. Thus polypropylene can bestabilized in an excellent manner by mixing it with 0.25% by weight ofdioctadecylsulfide.

The great advantage gained when applying such compositions ofantioxidants of group (a) and the cited costabilizers of group (b) doesnot lie solely in the fact that there took place a noticeable increasein the stability of the polyolefins, but that it had become possible toreduce the appropriate proportions of such compositions in View ofpossibly occurring discolorations of the synthetic plasties.

In the following table there is enumerated the brittle time (measured at140 C.) for polypropylene containing, in each case, 0.5% of thementioned stabilizer combination in the ratio of 1:1. As brittle timethere i indicated the time (in days) after which a compression moldedpolyolefin sheet having a thickness of 1 mm. breaks upon bending.

The process according to the invention can be applied with specialadvantage to low-pressure homopolymers or low-pressure copolymersobtained, for example, by the Ziegler process (cf. Raff-AllisonPolyethylene (1956), pp. 72-81). Here, the polymers are formed from anolefin in the presence of a catalyst prepared from a mixture of anorgano metallic compound and a compound of a heavy metal selected fromthe group of IVB to VIB of the Periodic Table.

The following example serves to illustrate the invention, but it is notintended to limit it thereto:

EXAMPLE Stabilization of polypropylene Embrittlement in days (at 140 C.)while the total concentration of stabilizer amounted to 0.5% (0.25% byweight of a condensation product of nonyl phenol and acetone and 0.25 ofthe synergist listed in the table):

Test results obtained with stabilizer mixtures composed of: 0.25% of acondensation product of nonyl phenol and acetone with the addition of0.25 of a costabilizer,

Concen- Brittle Oostabilizer tration, time at Shade after Percent Ctempering Didodeeyl sulfide 0. 25 40 Unchanged,

colorless. Dioctadecyl sulfide .1 0.25 40 0. Dieieosyl sulfide 0. 25 40Do. 1,2-bis-(octadecyl-mercapt ethane 0. 25 27 Do.1,4-bis-(oetadecyl-mereapto)- butane 0. 25 20 Do.Bis-(oetadecyl-mercapto)-diethylether 0.25 38 D0.1,2,4,5-tetramethyl-2,4-di

(dodeeyl-mercapto)-benzene 0. 25 20 Do. Tetra-(dodecyl-mercapto)-methane 0. 25 15 Do. Tetra-(octadecyl-mercapto)- ethane 0. 25 20 Do.Hexa-(dodecyl-mercapto)- ethane 0.25 15 D0. Condensation product ofnonyl phenol plus acetone (Without eostabilizer) 0. 25 3 Do.

Do 0.50 45 Do Furthermore, by way of comparison, the thio compoundswithout addition:

Didodecyl sulfide 0. 50 2 Do. 0.50 3-4 Do. 0.50 3 Do.

eapto)-butane 0. 50 1 Do. Bis-(oetadecyl-mercapto)- diethylether 0. 5023 D0. Tetra-(oetadecyl-mereapto)-ethane 0. 50 1 D0.Hexa-(dodeeyl-mercapto)- ethane 0. 50 1 Do.

As results from the table, the polypropylene is extraordinarily wellstabilized against embrittlement by the new stabilizer system. With theincorporation of the costabilizer having a synergistic action, theperiods of stabilization attained are many times the periods ofstabilization which were attained with the known stabilizers.

Analogous values are obtained when 0.25 by weight of2,6-di-tertiary-butyl-p-cresol, styrophenol or condensation products ofcamphene and phenols, containing 0.25% by weight of the costabilizerslisted in the above table, is applied for the stabilization ofpolypropylene or polyethylene.

We claim:

1. A composition of matter comprising (a) 2,6-ditertiary-butyl-p-cresol,(b) an organo sulfide selected from the group consisting of RSR, RS(CHS-R' and RSCH CH OCH CH SR', wherein R and R are alkyl nadicalscontaining 4 to 25 carbon atoms and n is an integer from 1 to 4, and (c)a normally solid polymer prepared by reacting a member of the groupconsisting of ethylene, propylene, butene, methylpentene and mixturesthereof in the presence of a catalyst prepared from a mixture of anorgano-metallic compound and a compound of a heavy metal selected fromthe group IVB to VIB of the Periodic Table, the total phenol and sulfidecompounds being present in an amount by weight of 0.001 to 5% in a ratioof 5:1 to 1:5 parts by weight.

2. A composition of matter comprising (a) a normally solid polymer of analpha-mono-olefin selected from the group consisting of ethylene,propylene and butene, (b) .005 to 2% by Weight of 2,6-di-tertbutyl-4-methyl phenol, and (c) from .005 to 2% by weight of a compoundhaving the formula RSR'SR wherein R is an alkyl radical having from 1220carbon atoms and R is an alkylene having from 1-4 carbon atoms, thephenol and sulfide compounds being present in a ratio of 1 to 5 parts byweight- (References 011 following page) References Cited by the ExaminerUNITED STATES PATENTS Skooglund 26045.7 Vincent 26045.9 Freidlander eta1. 26045 .7 Hawkins et a1 26045.7 Salyer 26045.95

6 2,995,539 8/1961 Barker et a1 26045.7 3,010,937 11/1961 Roos et a1.26045.7 3,020,259 2/1962 Schulde et a1 26045.7

5 LEON J. BERCOVITZ, Primary Examiner.

M. STERMAN, Examiner.

H. W. HAEUSSLER, H. LEVINE, Assistant Examiners.

Notice of Adverse Decision in Interference In Interference No. 96,113involving Patent No. 3,258,449, C. Heuck, O. Mauz, J. W'inter and F.Schulcle, POLYULEFINS STABILIZED \VITII 2,6-DITERTIARY BIITYL-p-CRESOLAND ORGANIC SULFIDES, final judgment adverse to the putentees wasrendered Mar. 26, 1968, as to claim 1.

[Ofliciczl G/zzefrfl July 2, 1968.]

1. A COMPOUND OF MATTER COMPRISING (A) 2,6-DITERTIARY-BUTYL-P-CRESOL,(B) AN ORGANO SELECTED FROM THE GROUP CONSISTING OF R-SR'',R-S-(CH2)N-S-R'' AND R-S-CH2CH2-O-CH2CH2-S-R'', WHEREIN R AND R'' AREALKYL RADICALS CONTAINING 4 TO 25 CARBON ATOMS AND N IS AN INTEGER FROM1 TO 4, AND (C) A NORMALLY SOLID POLYMER PREPARED BY REACTING A MEMBEROF THE GROUP CONSISTING OF ETHYLENE, PROPYLENE, BUTENE, METHYLPENTENEAND MIXTURES THEREOF IN THE PRESENCE OF A CATALYST PREPARED FROM AMIXTURE OF AN ORGANO-METALLIC COMPOUND AND A COMPOUND OF A HEAVY METALSELECTED FROM THE GROUP IVB TO VIB OF THE PERIODIC TABLE, THE TOTALPHENOL AND SULFIDE COMPOUNDS BEING PRESENT IN AN AMOUNT BY WEIGHT OF0.001 TO 5% IN A RATIO OF 5:1 TO 1:5 PARTS BY WEIGHT.